Difference between PAL and GAL?
Fred Heitkamp
I have been experimenting with VHDL and programming chips.
I've been wondering if there is any difference between
Generic Array Logic (GAL) chips and Programmable Array
Logic (PAL) chips, as far as the programmer is concerned?
For example, if I pick a 28 pin QFP, PAL22V10 as a target
device, when, in reality the device is a GAL22V10, will
there be a problem?
I appologize in advance if these questions are irratating
some of the more experience readers of this news group.
Fred Heitkamp
Clifford Ong
Fred Heitkamp wrote:
>
> I have been experimenting with VHDL and programming chips.
> I've been wondering if there is any difference between
> Generic Array Logic (GAL) chips and Programmable Array
> Logic (PAL) chips, as far as the programmer is concerned?
As far as programming is concerned, there is no difference,
for most small PLDs, whether you use a PAL or GAL device (from AMD
and Lattice, respectively.) I've used both types before and I have
never encountered any problems using a common programmer.
>
> For example, if I pick a 28 pin QFP, PAL22V10 as a target
> device, when, in reality the device is a GAL22V10, will
> there be a problem?
PLD devices like the 16V8 and 22V10 are considered industry-
standard and can be programmed by any programmer that supports them.
You will want to make certain though, that the pinouts are correct
since they tend to differ from package to package, and that the
device doesn't need any other special programming requirements (e.g.
different voltage.)
Cliff
--
Clifford Ong on...@rpi.edu
Advanced Imaging Systems Lab, ECSE Dept. http://www.rpi.edu/~ongc
Rensselaer Polytechnic Institute (518) 276-8207
Phil Ngai
In article <50mbau$p...@news-s01.ny.us.ibm.net>,
Fred Heitkamp <fhe...@ibm.net> wrote:
>For example, if I pick a 28 pin QFP, PAL22V10 as a target
>device, when, in reality the device is a GAL22V10, will
>there be a problem?
In general, PAL is a trademark for a particular type of device invented
by MMI, who were eaten by AMD. The term PAL is used by many companies.
The problem with the original PALs is that each macrocell was a fixed
type, either register or combinatorial as in a 16R4. AMD later provided
macrocells which were programmable as to registered or combinatorial in
the 22V10. Note that AMD calls the 22V10 a PAL.
Lattice came up with a part, the 16V8, which was FUSEMAP compatible
with any of the 16R4, 16R6, or 16R8. They had extra fuses to configure
this. They called this clever device a GAL. Unfortunately, their
marketing department thought GAL was such a wonderful name they went
and applied it to things like the 22V10 for which their original
enhancement was not applicable or usable.
Now AMD sells 16V8s and calls them PALs. I prefer to call them 16V8s.
However, you are particularly asking about programming. You should try
to get as close a match as possible to the device you are actually
programming because every manufacturer has different programming
algorithms and often there will be several different p.a. even for the
same "device" from the same company. For example, AMD makes a 22V10/4
and a 22V10/5 which use different p.a.
The accuracy of the p.a. is part of what you pay for in a programmer.
--
Fraser Warne
In article 16...@rpi.edu, Clifford Ong <on...@rpi.edu> opined:
>Fred Heitkamp writes:
>>
>> I have been experimenting with VHDL and programming chips.
>> I've been wondering if there is any difference between
>> Generic Array Logic (GAL) chips and Programmable Array
>> Logic (PAL) chips, as far as the programmer is concerned?
>
> As far as programming is concerned, there is no difference,
>for most small PLDs, whether you use a PAL or GAL device (from AMD
>and Lattice, respectively.) I've used both types before and I have
>never encountered any problems using a common programmer.
>
If you are talking about GAL22V10 & PAL22V10's, there is not much
difference between the two from a designers point of view. Both
have essentially identical capabilities.
However, there is a very big difference between a PAL22V10 and, say,
a PAL20L8. The 22V10 can emulate all 24-pinned PAL devices. The
16V8 can similarly emulate all 20-pinned PAL devices (PAL16R4's, etc.).
At a programmer, however, there is a big difference - you must select
the correct "target" device, and ensure that the jedec file that you
have generated is compatible with that device. Many programmers
have a "cross-programming" feature that lets you use a jedec for a
PAL20L8 (say) and cross-program it into a GAL22V10.
>>
>> For example, if I pick a 28 pin QFP, PAL22V10 as a target
>> device, when, in reality the device is a GAL22V10, will
>> there be a problem?
>
> PLD devices like the 16V8 and 22V10 are considered industry-
>standard and can be programmed by any programmer that supports them.
>You will want to make certain though, that the pinouts are correct
>since they tend to differ from package to package, and that the
>device doesn't need any other special programming requirements (e.g.
>different voltage.)
>
>Cliff
>
It is true that the 16V8 and 22V10 are industry standard, and any
programmer worth more than $0.02 should support them. It is also
true that a jedec file for a GAL16V8 can be programmed into a
PALCE16V8 (but be careful about 16V8 variants!). However, the fuse
map for a PALCE22V10 is different from that of a GAL22V10. If your
device to be programmed is a GAL22V10, and your jedec file is for a
PALCE22V10, your programmer will complain and won't program the PLD.
Even though these devices are identical from a designer's perspective,
you must generate a jedec file specifically for the device that you're
programming. I've learned this one the hard way! In most logic
compilers (Abel, Cupl, etc.) this is a very easy change to make just
before you go do do your compile.
-Fraser.
Mark Condit
different when generated for a Gal 16V8 then when it was for a Pal 16V8.
I'm curious what diferences are there? Thanks